Research On 3D Environment Perception And Obstacle Avoidance Of UAV In Urban Low-altitude Environment

Unmanned aerial vehicle(UAV)has advantages of high mobility,low cost,no risk of casualties,etc.,so it is widely used in military and civilian areas.However,due to the complexity of the city low-altitude environment and there are many unpredictable obstacles,when unmanned aerial vehicle is in the implementation of task,buildings,especially the high one,will be a security threat to UAV.Besides,the obstacle avoidance technology of UAV is not yet mature,flight of unmanned aerial vehicle can only be operated by human in urban low-altitude environment.Therefore,to achieve autonomous flying of unmanned aerial vehicle in urban low-altitude environment,there are two main issues to be resolved.First,how to make the UAV have the ability of 3D environment awareness.Second,how to make the unmanned aerial vehicle have the capability of obstacle avoidance to protect its own security.In order to solve these two problems above,the method of environment perception and obstacle avoidance autonomously for UAV is studied in this paper.The main contents are divided into three parts:(1)Constructing the stereo camera and unmanned aerial vehicle experimental system platform,and studying the method of three-dimensional environment reconstruction based on stereo vision;(2)Based on stereo vision,studying the method of obstacle detection,building recognition and 3D graphics modeling;(3)Studying the algorithm of path planning and the method of path tracking control in unknown environment,to achieve the goals of autonomous navigation,guidance and obstacle avoidance for unmanned aerial vehicle.this paper introduces the research status of 3D environment perception and obstacle avoidance for UAV in China and abroad,and the significance of this study.Then,the UAV experimental system platform,that we build up,is introduced,including hardware platform and software program architecture.And then 3D environment is reconstructed by using stereo camera and stereo matching algorithm.The algorithm of obstacle detection and building identification is designed,and the feasibility of the method of environment perception is verified by the experiment of autonomous environment perception using UAV platform in urban low-altitude environment.In order to achieve obstacle avoidance path planning,this paper proposes a force-carried variable-step-size rapidly-exploring random tree algorithm,and method of linear fitting and linear interpolation are used to smooth the planning path.Then,the dynamics model of the quad-rotor unmanned aerial vehicle and the path tracking controller is designed in this paper,and the effectiveness of the method of the obstacle avoidance is verified by the simulation of the obstacle avoidance flight finally.